The ONLINE system is for the 2019 returns only now ... if you need the PDF or .taxfile from 2018 you can get the by logging in and downloading them ...
To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)